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Uniform sediment flux or sediment balance
| Method indicator | ||
|---|---|---|
| Bottom-Up | Hybrid | Top-Down |
| YES | ||
Summary of key issues:
| Issue | Description |
|---|---|
| Description | In this type of model, sediment is moved within the estuary until a steady state is achieved when equal amounts on the flood and ebb tide. |
| Temporal applicability | Typically applied over the long-term (10-100 years). |
| Spatial applicability | Most often applied over the whole estuary as discrete areas of particular interest (e.g. tidal lagoon, channel, saltmarsh etc). |
| Links with other tools | Most recently applied to the ASMITA (Aggregated Scale Morphological Interaction between Tidal inlet and Adjacent coast) developed under ERP Phase 2. |
| Data sources | An understanding of the sediment dynamics including:
|
| Necessary software tools / skills | A top-down sediment flux/balance model and access to hydrodynamic information. The modelling requires a good understanding of the sediment transport regime within the estuary, long term evolution based on the equilibrium morphological state. |
| Typical analyses | Changes in estuary hypsometry (area and shape). |
| Limitations | An understanding of equilibrium regime theory based on the balance of sediment flux for a particular estuary or environment is extremely complicated and requires specialist knowledge. Calibration and interpretation of model results is limited to historic evidence based on previous bathymetry. |
| Example applications | Humber Estuary |
One of the earliest models to use the balance of net transport was a zero-dimensional model of a tidal lagoon by di Silvio (1989). The lagoon was schematised into just three components, tidal flat, littoral and tidal channel and the model was based on the idea that although locally and at any instant sediment transport is not in equilibrium, averaged over the system as a whole and a long enough period a relationship exists between the hydrodynamic quantities and the sediment concentrations.
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